In the prior art seat belt system of German Offenlegungsschrift 29 31 552, by Roger Woolnough, a belt buckle is retained in a sleeve which is mounted for pivotal movement to the vehicle floor and is urged by a spring into an upwardly pointing oblique position. When the seat bottom is being folded forwardly and the seat back is folded down to take its place on the vehicle floor, the seat back will urge the sleeves containing the belt buckles into a horizontal position. As soon as the seat back is raised up again, the sleeves with their belt buckles will automatically return to their upright position so that when the seat bottom is returned to its original position, the sleeves will be restored within the openings to their ready-to-use position.
The advantage of this particular prior art seat belt arrangement, as compared to the typical earlier arrangements in which the belt buckles were extending between the seat bottom and seat back were resting loosely on the seats, is the fact that one need not pay attention to the seat belts when the back seats are folded down and folded back, because they will not interfere with the folding operation and will return to their original position after the seats are folded back up again.
However, the seat belt arrangement according to DE-OS 29 31 552 is not suitable for those types of rear seats in which the seat back is stored by first folding the seat back forwardly and placing it on the seat bottom, and then folding the seat bottom and the seat back forwardly as one unit.
In order to ensure that the rear seats can be folded away in a vehicle having the type of folding mechanism mentioned above without interference by the seat belts and with no belt buckles remaining on the vehicle floor after the seats have been stored away, it has been proposed in accordance with Offenlegungsschrift, by Joachim Beitz, 29 28 341 that the belt buckles be fastened to the bottom of the seat backs. For this purpose, the back seat is provided with a downwardly directed hook which, when the seat back is in its normal upright position, will engage with an anchor plate attached to the vehicle floor. In this arrangement, the buckle is anchored to the seat back and the seat back to the vehicle floor. As the seat back is pivoted forwardly, it will first disengage from the anchor plate and can subsequently be folded down forwardly together with the belt buckles.